Directions
The meringues can be piped into four to six individual servings, rather than one large one.

Preheat the oven to 300°F. Line a baking sheet with parchment paper. To make the meringue, in a large bowl whip the egg whites with an electric mixer at high speed until foamy. Add the cream of tartar and whip until soft peaks form. Add the sugar in a slow steady stream, continuing to whip until the whites are very stiff and the sugar is almost dissolved, about 3 minutes. Fold in the cocoa. The cocoa does not have to be completely incorporated; some streaks are fine. With a rubber spatula, spread the meringue into a 7-inch circle on the baking sheet. Make a slight indentation in the center about 5 inches across. This will make a well for the filling. Bake for 25 minutes. Turn off the oven, but leave the meringue in the oven for 50 minutes to continue to dry out. Remove from the oven and cool to room temperature.

To make the filling, combine the cream, sugar, vanilla, and espresso powder in a large bowl. Whip with an electric mixer at high speed until soft peaks form. Fold in ½ cup of the chocolate chips. Spread the cream in the center of the meringue. Sprinkle the remaining chocolate chips on top. Serve immediately.